"We noticed that the Credit rewards for the new repeatable Heroic Space Missions (the ones you can do as many times as you want per day, not the Dailies) were too great and out of sync with how many credits we expected players to earn on average during normal gameplay. To account for this, rewards for these quests missions have been reduced to bring them more in line with the risk and cost of running Space Missions versus playing through the ground game’s content. We apologize to fans of the new Heroic Space Missions for this oversight and hope that the Credits and Commendations rewarded for the Daily quests are still found desirable enough to overcome the difficulty of these new challenges. Going forward, we will be keeping an active eye on this issue and others like it to make sure players are being rewarded correctly for the amount of effort they put into the game."
As the developer statement says, some of the space missions were not only repeatable multiple times a day, they gave a large amount of credits. Which means farming 12.5k would take merely minutes, allowing for people to attain large sums of credits quickly. This means credit farmers could easily make and sell their credits. It's a little annoying to not have seen any clarification before but understandable in this case.
They had good intentions, yes, but they went too far, they reduced the payoff to 1/10th
of the previous one. A 50% decrease would've been much more reasonable.